1. Field of the Invention
Exemplary embodiment of the present invention relate to a substrate of an electronic device, an electronic device including the substrate, and a measuring method of resistance at a connection portion.
2. Discussion of the Background
An electronic device, such as a display device, may include a substrate where a plurality of signal lines, electrodes, and thin film transistors are formed, and a driving circuit supplying a driving signal to the signal lines. The driving circuit may constitute an integrated circuit (IC) chip. The driving circuit may be mounted to the substrate of the electronic device or a flexible printed circuit (FPC) through various methods. For example, the driving circuit may be mounted on the substrate of the electronic device as a type of at least one integrated circuit chip (a chip on glass (COG) type), or may be mounted or integrated on a film such as a flexible printed circuit film (FPC) in which a plurality of conductive lead lines are formed on an insulating film such as a polyimide (a chip on film (COF) type) to be adhered to the substrate of the electronic device as a type of a tape carrier package (TCP).
Among processes for connecting the driving circuit chip of the COG type, or the film of the TCP type, and the substrate of the electronic device, a process of electrically connecting a pad portion of the signal line of the substrate and a driving circuit chip of the COG type or an output terminal of the TCP is referred to as an OLB process, that is, an outer lead bonding process. The driving circuit chip of the COG type, or the output terminal of the TCP type film, and the pad portion of the signal line of the substrate may contact each other by interposing an anisotropic conductive film (ACF).
Resistance of a connection portion of the driving circuit chip of the COG type, or the output terminal of the TCP type film, and the pad portion of the signal line of the substrate may include contact resistance between multi-layered thin films of the substrate and connection resistance between the driving circuit chip of the COG type, or the output terminal of the TCP type film, and the pad portion of the signal line of the substrate. The contact resistance in the connection portion may be determined by a material of the thin films that contact up and down or an interface characteristic therebetween, and the connection resistance may be determined by the anisotropic conductive layer and process conditions.
The resistance of the connection portion may be very important to normally drive the electronic device, and may be one of factors that cause a driving defect in a manufacturing process. If the resistance of the connection portion is high, distortion may be generated in a driving signal transmitted to the substrate of the electronic device such that the electronic device may be abnormally operated or an error may be generated in current consumption, manufacturing cost and manufacturing time may be increased, and yield may be decreased.